This invention relates to disk drives and, more particularly, to a method and apparatus for restoring the electromagnetic read/write heads of a disk drive to a location over a predetermined reference track on the corresponding surfaces of one or more disks located in the drive.
Previous methods of restoring a head to a predetermined reference track on a disk, normally referred to as track 0, involved the use of some kind of mechanical, electromagnetic or electro-optical sensor along the path of movement of the head carriage assembly. When the sensor detected the presence of the head-carriage assembly during movement in a direction toward the axis of rotation of the disk, such movement was stopped and the assembly was moved a predetermined number of tracks in the direction away from the axis of rotation. When this had been accomplished, the head would be located over the reference track.
The main disadvantage of this type of system is that positioning and alignment of the sensor is very critical. Any mechanical wear and vibrations, etc. that occur might adversely effect such alignment, causing the head to be restored to a track adjacent the desired reference track. Another disadvantage is that quite a bit of hardware is required.
It would be desirable, therefore, to provide a head restore method and apparatus which does not rely upon external sensors requiring critical alignments and the like.